Drinking to Thirst: Is It Enough?

Does the average person need more water than they are inclined to drink, even in a situation where water is lost in high volumes? The usual answer is "yes." In a recent review in Extreme Physiology and Medicine, researchers sought to find out if this common advice matches the facts.

What the research says:

Drinking to thirst is the most appropriate approach in most settings.

In special circumstances, drinking a prescribed amount of water can help combat dehyrdation and related problems.

Background

In their research, the investigators indicated the difficulty of actually identifying adequate hydration. While we might be inclined to say that your hydration status is simply how much water you have in you, it’s considerably more complex than that.

Distribution is one important factor for hydration. You might have plenty of total water in your body, but whether it’s in your cells or outside of your cells is of critical importance. Additionally, the composition of the solutes in your body’s water is just as important as how much water you have in your cells.

These factors make it hard to provide a cookie-cutter recommendation for how much water to consume. We have all heard of drinking eight glasses of water a day or some other fixed number. Many coaches also recommend drinking enough fluid to maintain your bodyweight during exercise. The researchers termed this more prescriptive approach to hydration anticpatory drinking.

Others would argue that we get thirsty when we need water, and if we drink when we are thirsty it should be enough to prevent problems. The researchers referred to this kind of approach as ad libitum drinking.

Research Design and Conclusions

The paper was a literature review. The researchers included 168 referenced materials to draw together their work. Think of it as a mini text book. Based on their review, the researchers concluded:

Ad libitum drinking seems appropriate in most exercise and environmental settings, but in special circumstances of obligatory hypohydration, anticipatory drinking is warranted.

There are a host of dangers that can arise from either chronic or acute hypohydration (insufficient water in the body) and hyperhydration (too much water in the body). However, in their review of the existing literature, the researchers found no existing scientific reason for the average person with access to food and water to heed the various prescriptive advice regarding how much to drink (i.e., eight cups per day or a similar guideline). They admitted that more research is needed on the topic, but currently many of the standard recommendations seem a little heavy-handed.

The researchers noted that if you’re in an extreme environmental situation, such as a hot day or in a high altitude, or are exercising for long periods of time, overhydration can become a serious problem. If you are too hydrated, the fluids of your body can become diluted. In these situations it is wise to consume electrolyte sources along with water, instead of water alone. But on most occasions, drinking when you are thirsty is the best way to stay hydrated.